Soundproof internal combustion engines



United States Patent [72] Inventor Fritz Freyn,

Graz, Austria [21] Appl. No. 697,896 [22] Filed Jan. 15, 1968 [45] Patented Sept. 29, 1970 [73] Assignee Hans List,

Graz, Austria [32] Priority Feb. 14, 1967 [33] Austria [31] Al,45l/67 [54] SOUNDPROOF INTERNAL COMBUSTION ENGINES 1 Claim, 8 Drawing Figs.

[52] US. Cl 123/4l.7, 123/4131, 123/4165, 123/41.69, 123/195, 181/33 [51] Int. Cl F0lp 1/02, FOlp 1/10, FO2f7/00 [50] Field ofSearch 123/41], 4l.65,41.69,198E,195C,41.31;181/33.4

[56] References Cited UNITED STATES PATENTS 2,123,358 7/1938 Grutzner ..123/198(E)UX 3,195,530 7/1965 Hfildnel ..l23/198(E)UX 3,358,668 12/1967 POStCIZll. ...l23/l98(E)UX FOREIGN PATENTS 567,567 2/1945 GreatBritain ..18l/33(.4)UX

OTHER REFERENCES Modern Plastics, October 1959, pages 94 and 95.

Primary Examiner-Al Lawrence Smith Anorney--Watson, Cole, Grindle and Watson ABSTRACT: An internal Combustion engine having a soundproofing enclosure and a cooling air blower with the enclosure consisting of at least two shells enclosing the engine in spaced relationship thereto Continuous soundproofing packing strips are provided which are of an elastic material and extending along the bearing surfaces of the shells with bolts interconnecting the shells and air ducts provided in a cavity between the shells and the outer surfaces of the cylinder block so that the entire cooling air will be directed over the outer surface of the cylinder block.

4 l l l l l l l l Patnted Sept. 29, 1970 Sheet 1 of 3 12' In 1/672 Z O/- m Z Z 'fiyn f 3,530,840 Patented Sept. 29, '1970 I Sheet 2 of3 Sheet 'IIIIIIIIIIAIIIIIIIIII, VIIIIIIIIIIII Fla 7 SOUNDPROOF INTERNAL COMBUSTION ENGINES While ensuring a certain reduction of the noise level of internal combustion engines, various conventional methods devised for that purpose have proved unsatisfactory both in view of the high expense and of a number of operational shortcomings involved.

Some types of internal combustion engines are known to be soundproofed by means of a sound-absorbing coating applied to the outside of the crankcase. However, the operations to be performed for that purpose, calling for a special treatment of the outer surface of the crankcase prior to the application of these coatings in order to ensure their proper adhesion and certain precautions to be taken to prevent the coating material from penetrating into the oil and water containers of the cylinder block, are both time-consuming and expensive.

Moreover, the sound-absorbing coating which must also comprise heat and oil-resistant materials, impairs heat abduction from the walls of the crankcase, thereby causing a considerable rise of the motor oil temperature. Consequently, the oil coolers must be oflarger dimensions.

Likewise, in some conventional types of internal combustion engines, such as the accommodation of the engines in for the purpose of absorbing the sound conducted through solids. However, similar crankcases are difficult to manufacture and therefore, expensive.

Other known methods of soundproofing internal combustion engines, such as the accomodation of the engines in sound-absorbing tents of their installation in special housings are fundamentally limited in application in view of the large .space required.

thereto so as to provide adequate sound insulation. This precludes sound radiation from the outer surface of the internal combustion engine in all directions. Only the connecting elements serving for the attachment of the engine to its supports remain uncovered. Consequently, the noise level of an internal combustion engine soundproofed in this manner is extremely low. The invention offers a considerable advantage .from the viewpoint of manufacture inasmuch as the elements of the shell construction can be made in serial production in a simple manner at low cost and readily mounted on the finished engines. Another advantage resides in the possibility of equipping existing standard types of not yet soundproofed internal combustion engines with the soundproofing shell construction according to the invention without major structural alterations.

Inasmuch as the shell is not called upon to carry or support any other members. and since its component parts are bound to be reinforced in view of their necessarily arcuate design, the shell may be of comparatively minor wall thickness ,andweight.

According to another feature of the invention, the shell body preferably comprises at least two sections interconnected by means of bolts and attachable to the cylinder block. This design offers the advantage of facilitating the assembly of ,the shell which in the embodiment of the invention shown by way of example consists of two halves provided with a number of aligned bolt bushes, since when the shell halves are bolted together the same are simultaneously secured to the cylinder block.

" According to another embodiment of the invention the shell sections attachable to the cylinder block carry sound-absorbing seats, such as sealing ledges of rubber or the like, on their contact surfaces with the cylinder block. These seats not only provide additional damping elements still further reducing the transmission of sounds to the shell to a considerable extent, but also serve to level any unevenness of the external surface of the engine used as a support for sections of the shell, so that these contact surfaces will not have to be especially machined. The elastic support of the shell by means of these sealing ledges offers the additional advantage of permitting the suppression of natural vibrations and resonance phenomena produced by the shell proper.

A preferred field of application of this invention are blowercooled internal combustion engines, wherein according to the invention the entire cooling air delivered by the cooling-air blower is directed within the cavity defined by the cylinder block and the shell over the oil-coated walls of the engine and over such additional members of the engine as may require cooling. This makes for particularly efficient cooling of the oil-coated engine walls as a result of which the oil temperature is reduced to such a degree that in certain cases, the conventional oil cooler may be dispensed with. Besides, this arrangement offers the possibility, for the first time, to direct cooling air also to such elements of the engine as usually remain uncooled, such as for example, the rocker box. Thus in addition to the soundproofing effect which is particularly noticeable in air-cooled internal combustion engines, improved cooling of the engine also makes for increased operational safety.

Needless to say that the feature of the invention hereabove described is also applicable to water-cooled engines where increased cooling of the cylinder block appears to be desirable. in that case, the required cooling air current can be produced either by means of the existing fan associated with the water cooling system or by a separate cooling-air blower.

According to another embodiment of the invention a particularly simple structural arrangement consists in partitioning the cavity between the cylinder block and the shell by means of sealing strips of an elastic material, such as rubber, attached to the shell and adjoining the cylinder block, so as to provide at least two separate air shafts for the conveyance of the air delivered to and discharged by, the cooling-air blower. For example, these sealing ledges may extend alongside the upper connecting flange of the crankcase, that is approximately at mid-level of the internal combustion engine, so as to contribute to the reinforcement of the shell. Since the elasticity of these sealing ledges levels any existing unevenness of the en gine surface out, the surfaces of these sealing strips in contact with the engine will not require special machining.

ln connection with fuel-injection-type internal combustion engines it will be preferable, according to the invention, to locate the fuel injection pump in a place of the cavity which is exposed to at least part of the cooling-air current. Thus the fuel injection pump is subject to intensive cooling, particularly if the port through which cooling air is admitted to the cavity of the shell is located in its immediate proximity, thereby positively precluding the formation of steam bubbles as occurs frequently particularly in tropical regions.

According to a further feature of the invention it is possible as a result of the passage of cooling air inside the shell, to make the latter ofa material of relatively poor thermal stability, such as synthetic resin. This is a considerable advantage not only in view of the resulting simplification and economy of the shell manufacturing process but also with regard to the particular sound-absorbing properties of the materials used for the purpose.

According to the invention, the inner surface of the shell of relatively noisy engines is preferably at least partly provided with a sound-absorbing coating. The sound-proofing of internal combustion engines thus achieved is of superior efficiency as compared with many conventional soundproofing methods. As a rule, this coating will only be applied in the area of highly sound-radiating engine parts, such as particularly in the area of the cylinders and cylinder-heads of air-cooled internal combustion engines.

Further details of the invention will become apparent from the following description of several embodiments of the invention with reference to the accompanying drawing in which:

HO. 1 shows a side elevation partly in section of an aircooled single-cylinder internal combustion engine according to the invention;

FIG. 2 a front view of the internal combustion engine according to FIG. I, both figures representing schematically simplified illustrations;

FIG. 3 is a partial side elevation partly in section of another embodiment of the invention as applied to an air-cooled internal combustion engine;

FIGS. 4 and 5 being partial cross-sectional views of the internal combustion engine shown in FIG. 3 on lines IV-IV and V-V respectively, of FIG. 3;

FIGS. 6 and 7 are horizontal cross-sectional views on lines VI-VI and VII-VII respectively, of FIG. 3; and

FIG. 8 shows a detail of the internal combustion engine according to FIG. 3 on line VIII-VIII of FIG. 3.

The air-cooled single-cylinder internal combustion engine illustrated in FIGS. 1 and 2 features a sound-proofing shell comprising two halves l and 2, the parting line 3 of which is located in the longitudinal central plane of the engine including the cylinder axis. In the area of the parting line 3 the halves l and 2 of the shell which are made of plastic material for example, comprise bolt bushes 4 aligned in pairs. In these places the two halves l and 2 of the shell are interconnected by means of bolts 5 extending through the bolt bushes 4. The shell is secured to the internal combustion engine by means of a compression joint produced simultaneously with the screwing together of the two halves 1 .and 2 of the shell. For that purpose, the halves l and 2 are provided with sound-absorbing sealing strips 6 to 9 of elastic material, such as rubber or the like, on their contact surfaces with the crankcase of the internal combustion engine. When the bolts 5 are tightened, these sealing strips are pressed on to the corresponding counter-surface of the internal combustion engine in such a manner as to provide both a seal and a means of leveling out any unevenness of the contact surfaces. By means of the sealing strips 6 to 9 sound radiation from the engine towards the elements of the shell is considerably reduced. Moreover, the sealing strips also attenuate occasional natural vibrations of the halves l and 2 of the shell.

In the embodiment shown the sealing strips 6 of the two halves 1 and 2 of the shell comprise the front end crankshaft flange 11, whereas the sealing strips 7 adjoin the flywheel flange 12 of the engine with a contact pressure extending in the direction of the crankshaft axis. The sealing ledges 8 rest on the crankcase 13 in the immediate vicinity of the cylinder 14 of the internal combustion engine. The sealing strips 9 adjoin the longitudinal edges of the cylinder-connecting flange of the crankcase l3 and partition the cavity defined by the shell and the internal combustion engine so as to produce an upper and a lower air shaft 15 and 16, respectively, for the air intake and exhaust.

Another shell member, designed as a lid 17 and comprising the upper portion of the cylinder head 10, is detachably secured to the top of the two halves l and 2 of the shell. This arrangement provides easy access to the cylinder head for the performance of various operations such as adjustments.

At the rear end of the shell facing away from the flywheel flange 12, the halves l and 2 of the shell present recesses which are open in the direction of the joint 3 and jointly defining the suction port 19 for the cooling air drawn in by the cooling blower 20 of the internal combustion engine (indicated by a dotted line in H6. 1), the cooling air admitted through port 19 being directed as indicated by an arrow over and above the fuel-injection pump 2] located directly behind the suction port 19 in two descending branch currents through the lower air shaft 15 over the sidewalls of the crankcase 13 to the blower 20. From there the cooling air passes upwards through ports (not shown) between the cylinder 14 and the flywheel flange [2 into the upper air shaft 16, where it sweeps over the cooling ribs of the cylinder 14 and of the cylinder head 18. Finally, the exhaust air, flowing upwards alongside the inclined partition of the shell enters an air baffle box 24 (shown in FIG. I only) secured to the front end of the halves l and 2 of the shell by means of bolts, for example, inserted in attachment bores 25 provided around the suction port 19. Following a single deflection the exhaust air then escapes into the open through an outlet 23 located on top of the air baffle box 24. The inner surface of the air baffle box 24 as well as the surface of the partition 22 facing the cylinder 14 of the internal combustion engine are provided with a sound-proofing coating 26. In an air-cooled internal combustion engine as hereinbefore described'this coating 26 serves primarily for the attenuation of the noise made by the incoming and outflowing blower air.

In principle, the internal combustion engine illustrated in FIGS. 3 to 8 is of the same design as the engine shown in FIGS. 1 and 2. Again, the shell comprises two halves l and 2' pro- 1 vided with bolt bushes 4' but open towards the front end of the engine facing away from the flywheel flange l2 and carrying a front end sealing strip 27. A perforated shell lid 28 resting on the sealing ledge 27 is mounted, with the interposition of a gasket 6', on the cover 10 of the engine secured to the crankshaft flange 11' by means of special bolts 34 which are threaded and provided with a central hexagon head 35. The lid 28 of the shell is provided with bores for the passage of the threaded extremities of the bolts 34 and clamped in the direction of the crankshaft flange 11' by means of nuts 36 screwed on to the bolts 34 with the interposition of rubber rings 33.

In order to make it possible for the engine to be mounted on a base 29 (shown in FIGS. 4, 5 and 6) the lower portion of the crankcase 13 remains uncovered by the shell. Consequently, the halves l and 2' of the shell terminate clear of the bottom of the crankcase 13' and abut with their sealing strips 7' against grooves 30 provided in the sidewalls of the crankcase 13. The arrangement of the lateral sealing strips 9' partitioning the cavity between the cylinder block and the shell so as to produce a lower and an upper air shaft 15' and 16' respectively, is illustrated particularly in FIG. 6.

The current path of the air drawn in by the blower inside the air shaft 15 is clearly indicated in FIGS. 4 and 7. After sweeping over the fuel-injection pump 21' and the walls of the crankcase 13' the cooling air passes through ports 31 of the crankcase into the suction chamber of the cooling blower 20' and finally via exhaust ports 32 of the blower housing into the upper air shaft 16' containing the engine cylinder 14.

I claim:

1. An internal combustion engine comprising a soundproofing enclosure and a cooling-air blower, the said enclosure consisting of at least two arcuate shell members elastically resting on a cylinder block of the engine and encompassing the same in spaced relation thereto, the said shell members adjoining each other alongside a common joint and comprising bolt bushes aligned in pairs in the area of the said joint, bolts extending through the said bolt bushes and interconnecting the said shell members and connecting the same with the cylinder block, a first group of sound-absorbing sealing strips of an elastic material arranged between the said shell members and their supports on the cylinder block and clamped between these elements by the prestressing force of the said bolts, an air inlet and an air outlet in the said enclosure, 21 second group of sealing strips of an elastic material secured to the inner surface of the said shell members and adjoining the outer surface of the said cylinder block, the sealing strips of the said second I 

